The central theme of this proposal is to examine the endocrine, immune and infectious mechanisms that are involved in preterm labor, both in the clinical setting and in experimental animals. The overall objective is to improve our comprehension of the forces which finally result in preterm labor and thereby bring about more rational approaches both to its prevention and its management. Specific studies include: 1) basic studies of biochemical alterations and placental enzymatic changes which occur prior to preterm labor; 2) examination of the role of fetal adrenal androgen secretion in preterm birth; 3) investigation of myometrial and decidual adrenergic and oxytocin receptor activity and their modulation by progesterone and estrogen; 4) determination of steroid content and receptor activity in uterine tissues and their interaction with adrenergic and oxytocin receptors; 5) study of the regulation of uterine prostaglandin synthesis and metabolism; 6) prospective clinical investigation of physical and endocrinologic changes that occur prior to preterm birth; 7) prospective assessment of serum immunosuppressive activity to determine if immunosuppressive factors play an etiologic role in preterm birth; 8) elucidation of the role of intrauterine infection in the pathogenesis of preterm labor; 9) accurate ultrasonic determination of fetal weight and size in low birth weight factors; 10) determination of the proper method to effect delivery of the preterm infant; 11) evaluation of proper anesthetic techniques to be used in management of preterm deliveries and anesthetic interactions with other medications used in treating preterm labor.